Protozoa are eukaryotes, one celled animals that are found in many parts of the ecosystem including soil, ponds, the digestive tract of insects (cockroaches) and the fore stomach of ruminants. Protozoa, thought to be the most ancient form of animals, consume bacteria (thought to be the most ancient form of life) as food.
Protozoa can be undesirable because of their ability to harbor pathogenic endosymbiants. After the outbreak of Legionnaires Disease, killing a number of people in Philadelphia, Pa. in the 1970's, it was discovered that the causative agent was a strain of Legionella pneumophila, a pneumonia causing bacteria that had survived as intracellular guests within in the protozoa thought to be living the cooling system of the building in which the Legionnaires gathered. Similarly, it has been reported that Salmonella, Mycobacterium bovis, Listeria monoytogenes and E. coli 0157:H7 can survive intracellularly in soil protozoa. Even as these soil protozoa become encysted in response to poor environmental conditions, the intracellular pathogens remain viable. In addition, studies have reported that intracellular pathogens can be resistant to bactericidal treatments such as chlorine (Appl. Environ. Microbiol., 1988, 54(12):3023-33).
Thus, free-living protozoa are believed to be able to act as a “Trojan Horse” and carry pathogenic endosymbiants. In this manner, the protozoa can act as a life-preserving capsule for the pathogen. Some studies suggest that some Salmonella, when ingested by rumen protozoa, developed the ability to resist the digestive processes of the protozoa and remain viable. Further, it was reported that the pathogen can become more virulent after living within the protozoa in comparison to counterparts that have not lived inside the protozoa.
Accordingly, a need exists for methods and compositions for reducing protozoal populations and/or killing protozoa.